I remember a question I asked my High School Biology teacher that had her puzzled....so I hope I can find an answer here.

I understand a virus has no source of energy such as mitochondrea powerhouses, etc. But the actions that take place when a virus comes near it's host seems to dictate otherwise, at least to me. When a virus comes near a host cell: it grabs and attaches itself to the cell, injects, and finally releases itself to float off into the abiss. My teacher's explanation of this attaching, injecting, and releasing itself is an automated mechanism that requires no energy, hence the lack of mitochondrea or other energy source.

But my question still stands, and I didn't want to ask her again for fear of getting into an argument during class.

Okay, so say I accept that there is no energy source available to the virus during the initial attack on the cell. But this process seems to be similar to that of a mousetrap. When the rat takes the cheese from the trap, an automated mechanism in the trap crushes the rat. Even though no energy was required to trip the mousetrap and catch the mouse, energy was required to set the trap....and this is the same problem I have with the virus.

If there is no energy required during the action of a virus attaching itself to a cell, injecting and releasing itself; then energy must have been used to "set the trap" in the virus. Right?

Another question that has me curious... Say a virus is much like an automated machine. Could we not build a machine to perform simple automated tasks that require NO energy? Based on the model of a virus's structure and behavior?

Thank you for reading and thanks in advance if you can help answer my questions.

There’s energy and then there’s "Energy," I guess. There is no additional external energy required for the binding of a virus to its receptor. It’s a spontaneous process in the thermodynamic sense. You could argue that the virus acquired energy from its prior host, but the virion itself carries nothing with it that generates or manipulates energy the way a cell or mitochondria does.

What sort of simple machine do you envision? The assembly of virions does require energy. That’s why viruses have to use a host to replicate; viruses lack metabolic/energetic machinery so they usurp their host’s. But this is not the same energetic question as binding to a receptor.

blcr11, the applications of building a machine that performs automated tasks as a result of a given stimuli can be applied to all aspects of technology, as these machines are currently in use today. But to build a machine that does its job without the use of fuel would be quite a breakthrough. The idea I had would be particularly useful in computer technology as the chips run based on an "On/Off" binary system.

So, the only energy required would be in the initial build of the system based on the characteristics of a virus. The system would then be able to run itself without the use of energy, other than the trigger and reset stimuli (which could possibly be a host-like system acting as the communicators to the virus.)

Can you imagine driving a car that requires no fuel at all? No more $80 dates at the gas pump! yay!

Maybe I'm getting in over my head.

Do you think something like this is one day possible? (Maybe not the car idea, although... )

The virus functions much like any other receptor-binding molecule: it takes advantage of molecular forces, such a van der Vaal's interactions, hydrophobic interactions, hydrogen bonding etc. So, the initial recognition of the target uses some of those forces (possibly other similar forces as well). However, the entry to the cells is often phagocytotic, or with enveloped viruses, fusion of the lipid membranes. These mechanisms use the host cell's energy sources - the virus kind of "fools" the host cell to think it is a useful particle or something, and the cell (again) does the work for the virus. And from there, all the energy required is stolen from the unfortunate host cell

EDIT: Oh, and what comes to the ability of viruses to bind their target in cold - I think the same rules apply than with many other molecular reactions, they get slower when it gets colder - naturyally when water freezes the activity pretty much stops. So I think viruses are capable of binding in cold, but far less efficiently. That in turn means, that the energy required in viral functions ultimately comes from thermodynamics. No heat = no energy, or so.

I think it is useful to contemplate the impossible. Every once in a while the impossible turns out not to be so impossible after all. Perhaps someday there will be a physics beyond “mere” thermodynamics, but so far there is no known process that violates the rule that it is impossible to create a heat engine with 100% efficiency, which is what you would have to do to create a car that runs without fuel. Doesn’t matter if you’re talking about mechanical systems or heat engines, the principles are the same. There is also the problem of mechanically connecting forces measured in the range of pN on the microscopic level of the individual molecule, to forces required to, say, throw a baseball. Tropomyosin/actin molecules in muscle do this all the time, of course, but this process requires ATP.

You may be interested in looking at things like DNA and/or quantum computers—which compute efficiently, but don’t in themselves move macroscopic objects around in space. A DNA computer has already been built (not that HP or Dell plans on selling one anytime soon), and they are working on prototype quantum dot computers. You might also be interested to read some papers on how people measure the properties of individual molecules of DNA or proteins. It’s not so straightforward and it’s taken over a decade to be able to do it reliably, but it can be done.

I just read an article on the thermodynamics of cellular systems (can't remember where) - at the moment, the mechanisms of classic thermodynamics can't be translated to cells, so at the moment we can't be completely sure that big machines are analogous to little biological ones.

Darby wrote:I just read an article on the thermodynamics of cellular systems (can't remember where) - at the moment, the mechanisms of classic thermodynamics can't be translated to cells, so at the moment we can't be completely sure that big machines are analogous to little biological ones.

Darby if you recall that article, please post it. This is a topic I have been pondering for quite sometime.